Spot beam satellites are effective for the transmission and reception of unicast and multicast data. In typical spot beam satellites, many smaller spot beams are used to provide coverage for a larger area that is defined by the union of the areas covered by each of the smaller spot beams. An example is depicted in FIGS. 1A-1C, which show how a number of spot beams, such as individual spot beam 102, provide satellite coverage over a large coverage area 104.
FIG. 2 is a simplified diagram of a return link of a typical bent pipe spot beam satellite system using a hub-spoke architecture. The depicted hardware connects one user beam to a gateway (GW) terminal. Multiple user terminals (UT's) 207 in a user beam 208 transmit data through a satellite 206 down to a GW terminal 226 in a GW beam 224. The bent pipe spot beam satellite 206 in this example is simplified but shows key elements of one return link signal pathway including a receive (Rx) antenna 212, a low noise amplifier (LNA) 214, a frequency converter 216, a high power amplifier (HPA) 218, and a transmit (Tx) antenna 220. Many UT's 207 can operate in the same user beam 208 by transmitting on the same frequency at different times (e.g., TDMA) or on different frequencies at the same time (e.g., FDMA). Return uplink signal 210 can then be a composite signal containing transmissions from a number of user terminals 207. A typical satellite 206 can have a number of these sets of pathway hardware connecting a number of user beams to a number of GW's.
A single user spot beam 208, as shown in FIG. 2, typically covers a small subset of a desired coverage area. Many user spots beams are employed in a manner similar to that depicted in FIG. 1 to provide service to a larger coverage area. Each of the spot beams is serviced by a GW terminal, and many spot beams may be serviced by the same GW terminal by use of different frequencies and/or polarizations. The total coverage area is the union of the areas covered by the individual user spot beams. This coverage area is the region where satellite service can be offered to customers. This coverage area is fixed and is selected during a satellite design process.
Satellite procurement, design, construction, launch, and test is a lengthy process. This process typically takes up to four years or more. The coverage area must be specified very early on in this process. In many instances, the desired coverage area is not well known at these early stages of satellite design. An educated guess must be made as to where the best coverage areas might be. If one chooses incorrectly, a coverage area may be selected that has few potential customers and/or a coverage area may be selected that does not include regions having many potential customers. These are clearly undesirable consequences.
This problem is further complicated by the long operational lifetime of satellites. Satellites typically have an operational lifetime of 15 years or more. During this time, target services areas can change dramatically. This can occur due to the development of ground infrastructure (e.g., wireless and fiber network build outs), re-purposing of the satellite, movement of the satellite to a different orbit slot, and the like. The satellite spot beams, however, and thus the coverage areas, are fixed in location and typically cannot be modified despite these changes.
Further, offered load at different spot beams can vary dramatically over short time periods. For example, a satellite system that covers the continental United States may experience busy hours on the East Coast that correspond to non-busy hours on the West Coast.
Thus, there is a need for improved spot beam satellites that allow for modification of capacity and coverage areas to adjust to short term demands and also throughout the operational lifetime of the satellite.